title: Inhibition of HIV-1 enzymes, antioxidant and anti-inflammatory activities of Plectranthus barbatus.
abstract: BACKGROUND
  Plectranthus barbatus is widely used in African countries as an herbal remedy to manage HIV/AIDS and related conditions.
  
  
  OBJECTIVE
  To investigate the HIV-1 inhibitory, anti-inflammatory and antioxidant properties of P. barbatus and thereby provide empirical evidence for the apparent anecdotal success of the extracts.
  
  
  METHODS
  Ethanolic extract of P. barbatus's leaves was screened against two HIV-1 enzymes: protease (PR) and reverse transcriptase (RT). Cytotoxicity of the extract was determined through measuring tetrazolium dye uptake of peripheral blood mononuclear cells (PBMCs) and the TZM-bl cell line. Confirmatory assays for cytotoxicity were performed using flow cytometry and real-time cell electronic sensing (RT-CES). The free radical scavenging activity of the extract was investigated with 2,2-diphenyl-1-picrylhydrazyl while the anti-inflammatory properties of the plant extract were investigated using a Th1/Th2/Th17 cytometric bead array technique.
  
  
  RESULTS
  P. barbatus extract inhibited HIV-1PR and the 50% inhibitory concentration (IC50) was 62.0 µg/ml. The extract demonstrated poor inhibition of HIV-1 RT. Cytotoxicity testing presented CC50 values of 83.7 and 50.4 µg/ml in PBMCs and TZM-bl respectively. In addition, the extract stimulated proliferation in HIV negative and positive PBMCs treated. RT-CES also registered substantial TZM-bl proliferation after extract treatment. The extract exhibited strong antioxidant activity with an IC50 of 16 µg/ml and reduced the production of pro-inflammatory cytokines indicating anti-inflammatory potential.
  
  
  CONCLUSIONS
  This is the first demonstration of the in vitro anti HIV-1 potential of P. barbatus including direct activity as well as through the stimulation of protective immune and inflammation responses. The low cytotoxicity of the extract is also in agreement with the vast anecdotal use of this plant in treating various ailments with no reported side-effects.
authors.affiliation: Department of Biochemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, Hatfield Campus, Pretoria 0002, South Africa.
authors.forename: Petrina
authors.initials: P
authors.lastname: Kapewangolo
authors.forename: Ahmed A
authors.initials: AA
authors.lastname: Hussein
authors.forename: Debra
authors.initials: D
authors.lastname: Meyer
mesh_terms: D000893:Anti-Inflammatory Agents / Q000009:adverse effects / Q000302:isolation & purification / Q000494:pharmacology*; D000975:Antioxidants / Q000009:adverse effects / Q000302:isolation & purification / Q000494:pharmacology*; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D016207:Cytokines / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D020834:Ethnopharmacology; D016333:HIV Protease / Q000009:adverse effects; D017320:HIV Protease Inhibitors / Q000009:adverse effects / Q000302:isolation & purification / Q000494:pharmacology*; D054303:HIV Reverse Transcriptase / Q000009:adverse effects; D015497:HIV-1 / Q000201:enzymology*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000821:virology; D016488:Medicine, African Traditional; D010936:Plant Extracts / Q000009:adverse effects / Q000302:isolation & purification / Q000494:pharmacology*; D018515:Plant Leaves / Q000737:chemistry; D031346:Plectranthus / Q000737:chemistry*
chemical_list: D000893:Anti-Inflammatory Agents; D000975:Antioxidants; D016207:Cytokines; D017320:HIV Protease Inhibitors; D010936:Plant Extracts; D054303:HIV Reverse Transcriptase; D016333:HIV Protease
keywords: Antioxidant; Cytokines; HIV-1 protease; HIV-1 reverse transcriptase; Plectranthus barbatus